1. Field of the Invention
The present invention relates to the field of mineral breakers, and more particularly, to replaceable wear tips for rotors in centrifugal mineral breakers.
2. Description of the Prior Art
Centrifugal mineral breakers, such as that described in U.S. Pat. No. 3,970,257, operate by feeding mineral material axially into a rotor from which it is expelled outwardly at high speeds into a housing surrounding the rotor. Some of the expelled material forms a protective rock lining in the housing. Mineral material subsequently ejected through discharge ports in the rotor impacts the protective rock lining. Similarly, a protective rock lining forms inside the rotor protecting most of the inside surfaces of the rotor, except for surfaces located near the discharge ports through which mineral material is ejected from the rotor. The parts of the rotor near the discharge ports are subjected to severe wearing forces from the stream of mineral material being ejected. Accordingly, discharge ports are normally provided with wear tips to protect the port edge from rapidly deteriorating. Typically, a wear tip is placed vertically across the width of each discharge port. The wear tip forms a hardened lip which protects the rotor from erosion caused by the rock exiting with extreme force and velocity.
Commonly, wear tips have a generally square profile and can be dropped or bolted into place. In the drop-in style, a square-shaped socket is provided in the bottom ring of the rotor in which the wear tip is seated. A top part of the wear tip is held in place in a square aperture in the top ring of the rotor. For bolted designs, numerous arrangements are possible to fix the wear tip in place. The wear edge of the tip is that corner most exposed to abrasion from streaming mineral material. The wear edge is generally provided with an abrasion resistant insert, typically made from tungsten carbide, which is much more effective at withstanding the wear forces of the stream of material. The main body, or carrier portion, of the wear tip is constructed of steel or cast iron which is much more susceptible to erosion than the insert. The insert generally bears a uniform rectangular profile through its longitudinal dimension and fits in a conforming channel or recess in the wear edge of the tip. To prevent the insert from slipping out of the insert, it is held in place with an industrial adhesive. Frequently, as an added measure of assurance, a bead of weld is applied in the recess the top and bottom of the insert in case the adhesive fails. Often an insert is assembled from several pieces which are fitted in end-to-end abutment in the recess. Unfortunately, this leaves joints between the individual pieces which weakens the bond of each piece to the carrier and leaves a space into which fine particulate matter inserts itself between adjoining pieces. As a result individual pieces of insert material have been known to separate and creep out of the recess thereby exposing the wear tip to erosive damage.
The primary objective for wear tips is to provide sufficient longevity that the rotor will be protected until it can be observed during a regular maintenance check that the tips have become damaged so that they may be replaced. Wear tips experience greatest wear near the middle of the span across the discharge port and it has been found that unused portions at the top and bottom of the tungsten carbide insert are routinely discarded when the center of the insert becomes fully eroded or loses its usefulness through breakage or detachment. Applicants have observed that under typical wear patterns, approximately forty to fifty percent of the original tungsten carbide is not utilized and is discarded as waste in this manner when the middle of the insert is no longer useful. Since tungsten carbide is relatively expensive, discarding nearly half of the insert is economically inefficient.